高等学校化学学报

高等学校化学学报 ›› 2013, Vol. 34 ›› Issue (1): 192.doi: 10.7503/cjcu20120219

• 物理化学 • 上一篇    下一篇

添加气对非平衡等离子体转化低碳烷烃的影响

董洁1, 王丽1, 赵越1, 张家良2, 郭洪臣1   

  1. 1. 大连理工大学化工学院催化化学与工程系及精细化工国家重点实验室, 大连 116023;
    2. 大连理工大学物理与光电工程学院, 大连 116023
  • 收稿日期:2012-03-14 发布日期:2012-12-31
  • 通讯作者: 郭洪臣,男,博士,教授,博士生导师,主要从事等离子体催化,分子筛催化和低碳选择活化方面的研究.E-mail:hongchenguo@163.com E-mail:hongchenguo@163.com

Effect of Additive Gases on Light Alkanes Converting Under Dielectric Barrier Discharge

DONG Jie1, WANG Li1, ZHAO Yue1, ZHANG Jia-Liang2, GUO Hong-Chen1   

  1. 1. Department of Catalytic Chemistry and Engineering, School of Chemical Engineering & State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116023, China;
    2. Department of Physics and Optoelectronic Engineering, Dalian University of Technology, Dalian 116023, China
  • Received:2012-03-14 Published:2012-12-31

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被引次数

12

摘要：

在常压下, 研究了添加气的种类(N2, He, Ar, H2, NH3, CO和CO2)对介质阻挡放电低碳烷烃(甲烷、 乙烷和丙烷)转化制低碳烯烃的影响. 结果表明, 以甲烷或乙烷为原料时, N2, He, Ar和CO的引入有利于提高原料的转化率和总烯烃的选择性; 而CO2, H2和NH3的引入对甲烷、 乙烷的转化率无明显影响, 但H2和NH3的引入会使总烯烃的选择性显著降低. 以丙烷为原料时, 所研究的添加气均可提高丙烷的转化率, 而只有CO的引入可提高总烯烃选择性. 综上所述, 80%(摩尔分数) CO添加量最有利于低碳烷烃转化成低碳烯烃, 对应的甲烷、 乙烷和丙烷的转化率分别提高了14.4%, 17.6%和42.8%, 总烯烃的选择性分别提高了19.9%, 25.0%和11.9%. 以CH4为例, 通过对放电电流波形和等离子体区物种的发射光谱(OES)研究发现, 引入CO能显著增加等离子体的电子密度, 并且体系中出现激发态O*物种(777.5和844.7 nm), 这种O*物种能够促进C-H键的断裂, 有利于烯烃的生成. 因此, 等离子体区电子密度的增加和激发态O*物种的出现可能是CH4-CO体系中CH4有效转化的主要原因.

关键词: 低碳烷烃, 添加气, 等离子体, 低碳烯烃, 发射光谱

Abstract:

At atmospheric pressure, the influences of different types of additive gases(N2, He, Ar, H2, NH3, CO, CO2) on the transformation of low carbon alkanes(CH4, C2H6 and C3H8) to light alkenes via the dielectric barrier discharge non-equilibrium plasma(DBD plasma) method were investigated. Results show that the additive gases have different effects on the reaction. For CH4 or C2H6, the conversion and selectivity of feedstock increase with the introduction of N2, He, Ar, CO. While CO2, NH3 and H2 have no obvious effect to conversion of feedstock but NH3 and H2 inhibit the selectivity obviously. As for C3H8 feedstock, the conversion can be enhanced by all the additive gases mentioned above, while the selectivity decreased in different degrees except CO. Among these additive gases, 80%(molar fraction) CO exhibits the best activity both for the feedstock conversion and selectivity of total alkenes. The conversion of CH4, C2H6 and C3H8 increase by 14.4%, 17.6% and 42.8%, respectively, and the corresponding selectivity of total alkenes increase by 19.9%, 25.0% and 11.9%, respectively. Studies on in situ optical emission spectroscopy(OES) and current waveform of discharge show that the introduction of CO can not only increase the electron density of plasma, but also generate the excited oxygen atoms(777.5 and 844.7 nm), the latter can effectively facilitate the C-H cleavage of methane to the formation of ethylene. Therefore, the existence of excited oxygen atoms and the increased electron density of plasma may be the main reasons to cause the effective transformation of methane to light alkenes when CO as additive gas.

Key words: Light alkane, Additive gas, Plasma, Light alkene, Optical emission spectroscopy

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